Headgear suspensions are worn in a variety of environments and for various purposes. Headgear suspensions allow protective equipment, such as face shields and helmets, to be suspended from the head. A common element of headgear suspensions is the headband, usually fabricated from a thin band of plastic material formed into a generally circular shape with ends overlapping and joined at the back of the head.
Various means have been devised to adjust the girth of the headband to the extent necessary to fit the variety of head shapes and sizes of different wearers. One such means is illustrated in U.S. patent application Ser. No. 11/316,232 to Rogers, et al., which describes a headband having a flexible band that can be manually adjusted by the wearer. The two ends of the band are joined by a tab and slot arrangement. One or more tabs formed on one end of the band are inserted into one or more slots in a series of parallel slots formed in the other end of the band. The band is generally circular in shape with the selected slot(s) corresponding to a smaller or larger circumference for the headband.
A second method for adjusting the circumference of a headband is illustrated in U.S. Pat. No. 4,942,628 to Freund. According to Freund, the ends of a flexible band are connected, held in place, and adjusted by a ratchet mechanism. The ratchet adjustment knob has a set of cog teeth, which act on teeth formed in overlapping ends of the headband. Turning the knob one direction pulls the strap ends closer together, and turning the knob the other direction forces the ends apart.
The ratchet adjustment is generally preferred over the manual adjustment means because the headband can be adjusted while on the head of the wearer. The knob, however, must be large enough to be grasped and turned by the wearer's fingers, which may be covered with gloves.
The size and weight of the ratchet mechanism and the knob have disadvantages in some applications. For example, in order to access the knob in a protective helmet, the knob must be positioned below the edge of the helmet shell. Alternatively, the helmet shell must be significantly distanced from the wearer's head to provide room for the knob and to allow the wearer's fingers to operate the knob inside the helmet shell volume.
U.S. Pat. No. 2,747,191 to Hoffmaster describes a headgear adjustment mechanism that includes a worm attached to a headband end. During operation of the worm, the worm crawls along another headband component, thereby adjusting the headband circumference in a manner similar to the operation of a worm drive hose clamp. Hoffmaster's worm is exposed along the length of the headband and moves around the perimeter of the headband as it is adjusted.
Considering the above, there is a need for a headgear adjustment mechanism that can be operated by the wearer while on the wearer's head and that is smaller, easier to operate, and lighter-weight than conventional ratchet mechanisms.